This invention relates to a process for the oxidation of unsaturated amines to unsaturated nitriles especially the oxidation of allylamine and methallylamine to acrylonitrile and methacrylonitrile respectively.
Polymers derived from unsaturated nitrile monomers such as acrylonitrile, methacrylonitrile, vinylidene cyanide, etc., are well known in the art. Of this class of monomers, acrylonitrile is presently the most important and is used in making a variety of commercial products e.g., butadiene-acrylonitrile copolymer rubbers, acrylonitrile-butadiene-styrene (ABS) copolymers and acrylic textile fibers.
Several means of producing acylonitrile have been proposed including dehydration of ethylene cyanohydrin, the direct reaction of acetylene and hydrogen cyanide and the catalytic amination of propylene followed by dehydrogenation of the proprionitrile so produced.
One of the more effective routes that is widely practised is the catalytic ammoxidation of propylene.
These processes, however, have the disadvantage of producing troublesome by-products and some, particularly the last mentioned, require the use of very expensive high pressure and high temperature equipment.
A further alternate process was disclosed in British Pat. Specification No. 570,835 granted to Shell Development Company on July 25, 1945. This process is one for the production of unsaturated nitriles from the corresponding unsaturated amine by reacting the amine with oxygen in the presence of a silver oxidation catalyst at a temperature of at least 450.degree.C. The process is essentially a vapor phase reaction in which a mixture of the amine vapor, oxygen and an inert carrier gas are passed over a metal-alloy catalyst bed at about 500.degree.C. This process has the disadvantage of requiring expensive and complex equipment and high temperatures.
A further development of the route from unsaturated amine to unsaturated nitrile is provided in U.S. Pat. No. 3,719,701 in which the amine is reacted with molecular oxygen in a solvent containing cuprous and cupric ions, the solvent being a nitrogen base. This process has many advantages in its simplicity, its relative freedom from undesirable by-products and its adaptability to continuous operation. It does, however, have the disadvantage that the yields obtained are quite low, the figure given for the conversion of allylamine to acrylonitrile using a cuprous chloride catalyst being 43.8%.
We have now discovered a modification of the above process by which the yield of nitrile from such a reaction can be substantially increased.
Accordingly it is an object of this invention to provide an improved process for the oxidation of an unsaturated amine to an unsaturated nitrile.